Hydrocarbon lubricants, such as hydrocarbon oils, are susceptible to oxidation and varnish formation during normal operation of the lubricant systems. The petroleum industry over the years has eliminated most of the impurities from crude oil via hydrocracking or produced synthetic hydrocarbons to minimize oxidation problems later on. More recently, companies have developed varnish prediction test methods and varnish removal filters to filter out the soluble and insoluble varnish in lubrication systems. In spite of such efforts, it still becomes necessary after a period of time to address the problems associated with sludge and varnish. Further, varnish deposits onto machine parts causing the parts to stick and interfere with operation of a machine. This interference causes unplanned failures, downtime, and loss of equipment reliability.
Both draining and refilling a lubrication system and use of a varnish removal filtration system are expensive options and cannot guarantee that varnish is not deposited onto working machine parts. While there has been progress in slowing the oxidation process, predicting the varnish formation, and removing some of the varnish via filtration, varnish can only be removed by filtration if the oil makes its way back to the filter. Oil that is out in the lines of a lubrication system can continue to degrade and deposit varnish, causing problems with operation of machinery. One proposed solution is a hydrocarbon-based lubricant with polyether as described in U.S. Patent Application Publication No. 2013/0261035 or International Patent Application Publication No. WO 2013/148743, each of which is incorporated by reference in its entirety.
Further, today's modern machinery is designed for continuous operations. The stopping of a machine causes several problems for today's manufacturer. The interruption of production causes lost revenue and difficulty with machinery restarting. Manufactures are interested in a flushing technology which does not interfere with 24/7 production requirements. Scheduled downtime is very limited to the most critical maintenance practices and leaves little time for proper oil servicing. This has become very challenging with the typical oil flushing models developed through ASTM D6439, which is discussed below.
Today's modern machinery is designed for optimum speed and efficiencies. These machines have ability to measure their own performance through onboard sensors. These sensors may track system speed, temperature, part quality, and machine total output. Hydraulic and lubricating oils are key to system performance. The need to keep these highly sophisticated hydraulic systems free of contaminants is directly related to the total output of these machines.
The process of flushing a lubricant system requires the flow of a fluid—the current in-service fluid, a sacrificial flush fluid, or a modification of one of these two. The flushing process is defined by ASTM D6439 (Standard Guide for Cleaning, Flushing, and Purification of Steam, Gas, and Hydroelectric Turbine Lubrication Systems). According to ASTM D6439, there are 4 types of flushing approaches: displacement flush, high velocity flush, surface active cleaner flush, and solvent cleaners. A displacement flush utilizes a displacement flush oil of the same chemistry as the operating oil. System pumps and flow channels are utilized to circulate the displacement flush oil. Side stream filtration is recommended to improve flush effectiveness. Regarding high velocity flush, the primary requirement for successful oil flush is a high oil velocity, at least three to four times normal system velocity, within the system. Wherever possible, turbulent flow should be achieved in system pipes. A Surface Active Cleaner flush requires a cleaning solution to be added to the system as part of the flushing process. It also requires that this cleaning agent be completely removed before addition of new fluid. Solvent Cleaners utilize a solubilizing solvent be added to the operating fluid to aid in removal of the impurities. These solubilizing agents can be removed with the old fluid or maintained is the system after the flush has been completed, depending on their chemistry and the flushing operations.
The standard operation of flushing can apply heat and/or filtration during the flushing operation to aid in the cleaning process. Most often, the operations are performed by shutting-down the unit to be flushed down during the flush. This means the production operations of the unit can be down for 3-7 days. This is especially the case when the first three types of flushing operations are utilized. The current state of the art is to follow the D6439 Standard methodology. The problem with this is the down-time required. This is a very costly endeavor, and improvements or work-arounds are constantly being investigated.